Gas exchange and Digestion Flashcards
Surface area : Volume ratio
relationship between the size of an organism or structure and its surface area to volume ratio plays a significant role in the types of adaptions an organism will have.
allows transport across surface more efficient in organisms.
calculate
-surface – multiply length by width then times by how many sides.
-SA:VR calc the volume- normally length x width x height.
small organisms SA:VR
-small organisms have a very large surface area in comparison to their volume
-this means there is a big surface for the exchange of substances, but there is also smaller distance from the outside of the organism to the middle of it
- as a result very small organisms can simply exchange substances across its surface by diffusion.
larger organisms SA:VR
why does larger organisms having a higher metabolic rate mean that they need specific adaptions.
-larger organism = smaller the SA compared to ratio
-therefore larger the distance from the middle to the outside
-larger organisms will typically have a higher metabolic rate, which demands efficient transport of waste out of cells and reactants into cells.
because of this they have adaptions that help make their exchange across surfaces more efficient.
some examples that larger organisms may have to allow efficient exchange across surfaces
-villi and microvilli - absorption of digested food
-alveoli and bronchioles- for efficient gas exchange in animals.
-spiracles and tracheoles - for efficient gas exchange in terrestrial insects
-gill filaments and lamellae- for efficient gas exchange in fish
-thin wide leaves- for efficient gas exchange in plants
-many capillaries- for efficient exchange at tissues.
the key structures in the human gas exchange system
labelled diagram in notes
-alveoli
-bronchioles
-bronchi
-trachea
-lungs
what do we need to know for ventilation within the human gas exchange system
labelled diagram in notes
-diaphragm
-intercostal muscles
ventilation
labelled diagram in notes.
-exhaling and exhaling in humans
-controlled by the diaphragm muscle and the antagonistic interaction between the external and internal intercostal muscles.
how does the diaphragm and antagonistic internal and external muscles work to cause inspiration and expiration.
external intercostal muscles.
inspiration- contract to pull the ribs up and out
expiration - realx
how does the diaphragm and antagonistic internal and external muscles work to cause inspiration and expiration.
internal intercostal muscles
inspiration - relax
expiration- contract to pull the rib down and in
how does the diaphragm and antagonistic internal and external muscles work to cause inspiration and expiration.
diaphragm
inspiration - contracts to move down and flattens
expiration - relaxes to move up and dome.
how does the diaphragm and antagonistic internal and external muscles work to cause inspiration and expiration.
air pressure in the lungs
Inspiration- initially drops as air moves in it rises above atmospheric pressure
Expiration - initially greater than atmospheric pressure
Drops as air moves out
how does the diaphragm and antagonistic internal and external muscles work to cause inspiration and expiration
Lung volume
Inspiration-increases
Expiration - decreases
how does the diaphragm and antagonistic internal and external muscles work to cause inspiration and expiration
Movement of air
Inspiration- air moves into lungs as the atmospheric pressure in the thorax is higher than that of the atmosphere
Alveoli when is the air received and where is it came from
Diagram in notes
-once the air has travelled down the trachea bronchi and bronchioles to the alveoli gas exchange occurs between the alveolar epithelium and the blood.
Alveoli
Adaptions
Diagram in notes
-tiny air sacs
-300 in each human lung (large amount)
Creates a larger surface area for gas exchange
-the alveolar epithelial cells are very thin to minimise diffusion pathway
-each alveolus is surrounded by a network of capillaries to remove exchanged gases and therefore maintain a concentration gradient
Gas exchange in fish
-fish are waterproof and they have a small SA:VR this is why the require a gas exchange surface (gills)
Fish obtain oxygen from the water but there is 30 times less oxygen in water than in air
So they have a special adaption (countercurrent flow) to maintain the concentration gradient to enable diffusion to occur.
Fish gill anatomy
Diagram in notes
-there are four layers of gills on both sides of the head
These gills are made up of stacks of gill filaments
Each gill filament is covered in gill lamellae positioned at right angles to the filament this creates a larger surface area
When fish open their mouths water rushes in and over the gills and then out through holes in the sides of their head.
Adaptions for gas exchange in fish
- to create a larger surface area to volume ratio for diffusion there are many gill filaments covered in many gill lamellae
-there is a short diffusion distance due to a capillary network in every lamellae and all gill lamellae are very thin
-the concentration gradient is maintained by the countercurrent flow mechanism
What is Countercurrent flow mechanism
Diagram in notes
-when water flows over the gills in the opposite direction to the flow of blood in the capillaries
What does countercurrent flow ensure
Diagram in notes
That equilibrium is not reached
This ensures that a diffusion gradient is maintained across the entire length of the gill lamellae
gas exchange in terrestrial insects
-exoskeleton =made from hard fibrous material for protection
and a lipid layer to prevent water loss.
-therefore they need a gas exchange system.
-they do not have lungs but instead have a tracheal system.
the tracheal system
whats involved?
- trachea
-tracheoles
-spiracles
tracheal system
spiracles
-round valve like openings
-running along the length of the abdomem.
-oxygen and carbon dioxide enter and leave via the spiracles
-the trachea attaches to these openings
tracheal system
the trachea
-a network of internal tubes
-the tubes have rings of cartliage (tough connective tissue) within them to strengthen them and keep them open.
tracheal system
tracheoles
trachea branch into smaller tubes called tracheoles
-these extend through ought all the tissues in the insect to deliver oxygen to all respiring cells
gas exchange in terrestrial animals
three key adaptions in terrestrial insects
-a larger number of fine tracheoles - larger surface area
-the walls of the tracheoles are very thin and there is a short diffusion distance between spiracles and tracheoles- a short diffusion pathway
-the use of oxygen and the production of carbon dioxide sets up steep concentration gradient.
movement of gases - insects
by diffusion
-gas can exchange by diffusion
-as when cells respire
they use up oxygen
and produce carbon dioxide
this establishes a concentration gradient from the tracheoles to the atmosphere.
movement of gases insects
mass transport
method of gas exchange
in which insect contracts and relaxes their abdominal muscles to move gases in mass
movement of gas - insects
flight
-when the insect is in flight and the muscle cells start to respire anaerobically to produce lactate.
-this lowers the water potential of the cells
-therefore water moves from the tracheoles into cells by osmosis
-this decreases the volume in the tracheoles and as a result more air from the atmosphere drawn in
limiting water loss in terrestrial insects.
-water evaporates of the surface of terrestrial insects
the adaptions of gas exchange surfaces provide ideal conditions for evaporation
-therefore they need additional adaptions to reduce water loss by evaporation.
insect adaptions to prevent water loss
-insects have a small surface area to volume ratio to minimise water loss by evaporation
-insects have a waterproof exoskeleton
-spiracles ( from which gases enter and water evaporates) can open and close to reduce water loss.
gas exchange in plants
reducing water loss in plants
-xerophytic plants are adapted to survive in environments with limited water.
they have structural features to enable the efficient gas exchange to occur whilst also limiting water loss.
for example
marram grass.
adaptions of xerophyte
-curled leaves to trap moisture to increase local humidity
-hairs to trap moisture to increase local humidity
-sunken stomata to trap moisture to increase local humidity
-thicker cuticle to reduce evaporation
-longer root network to reach more water.
digestion definition
large biological molecules are hydrolysed into smaller molecules that can be absorbed across cell membranes.
digestion of carbohydrates
- starts in the mouth
-continues to duodenum - completed in the ileum
digestion of carbohydrates
what do they require
require more than one enzyme to hydrolyse them into their constituent monosaccharides:
-amylases
-membrane bound disaccharides.
digestion of carbohydrates
amylase
-produced by the pancreas and salivary glands
-hydrolyses polysaccharides into disaccharide maltose by hydrolysing the glyosidic bonds
sucrase and lactase are membrane bound disaccharides that hydrolyse sucrose and lactase into monosaccharides
digestion of proteins
how are they hydrolysed
-proteins are large polymer molecules that can be hydrolysed by three enzymes :
1. endopeptidase – hydrolyse peptide bonds between amino acids in the middle of the polymer chain
- exopeptidase- hydrolyse peptide bonds between amino acids at the end of the polymer chain
3.membrane-bound dipeptidases –hydrolyse peptide bonds between two amino acids
protein digestion
starts in the stomach
continues in the duodenum
fully digested in the ileum.
digestion of lipids
what are they digested by
-lipids are digested by lipase and the action of bile salts
digestion of lipids.
where is lipase produced
-pancreas
-can break the ester bonds in triglycerides to form the monoglycerides and fatty acids.
digestion of lipids
where are bile salts produced
-liver
-emulsify lipids to form tiny droplets and micelles
- this increases the surface area for lipase action.
what two stages are involved in digestion of lipids.
- physical - emulsification and micelle formation
2.chemical - lipase
physical stage of lipid digestion
emulsification and micelle formation
-lipids are coated in bile salts to create emulsion
-many small droplets provide a larger SA to enable faster hydrolysis by lipase
chemical (lipase) stage of lipid digestion
lipase hydrolyses lipids into glycerol and fatty acids ( some monoglycerides)
micelles
-water soluble vesicles formed from fatty acids, glycerol, monoglycerides and bile salts
-the bile salts make the fatty acids and micelles water soluble
what do micelles do
-deliver the fatty acids, glycerol and monoglycerides to the epithelial cells of the ileum for absorption
process of absorption
diagram in notes to follow
-being non polar and lipid soluble the fatty acids and monoglycerides can enter the epithelial cell via simple diffusion
-fatty acids and monoglycerides (resulting from fat digestion ) leave micelles and enter the epithelial cells
-fatty acids link to form triglycerides
look at notes with this card.
absorption in mammals
-absorbed across the cells lining the ileum
- the ileum wall is covered in vili, which have thin walls surrounded by a network of capillaries and the epithelium of the small intestines is lined by even smaller microvilli.
(diagram in notes as a visual)
these features maximise absorption by increasing the surface area, decreasing the diffusion distance and maintaining a steep concentration gradient.
EOU- key structures to know in the human gas exchange system.
alveoli
bronchioles
bronchi
trachea
lungs
EOU- key structures to know for ventilation
-diaphragm
-ribs
-intercostal muscles.
EOU- ventilation
is inhaling and exhaling in humans
This is controlled by the diaphragm muscle and the antagonistic interaction between the external and internal intercostal muscles.
EOU - external intercostal muscles
inspiration
contract to pull the ribs up and out
EOU - external intercostal muscles
expiration
Relax
EOU- Internal intercostal muscles inspiration
relax
EOU- internal intercostal muscles
expiration
contract to pull the rib down and in.
EOU- diaphragm
inspiration
contracts to move down and flattens
EOU- diaphragm
expiration
relaxes to move up and dome
EOU- air pressure in lungs
inspiration
initially drops
as air moves in it rises above atmospheric pressure.
EOU- air pressure in lungs
Expiration
initially greater than atmospheric pressure
drops as air moves out.
EOU-lung volume
inspiration
increases
EOU- lung volume
expiration
decreases
EOU- movement of air
inspiration
air moves into the lungs , as the atmospheric pressure is higher than that of the thorax
EOU- movement of air
expiration
air moves out of the lungs, as the pressure in the thorax is higher than that of the atmosphere.
Alveoli EOU
Once air has travelled down the trachea, bronchi and bronchioles to the alveoli, Gas exchange occurs between the alveolar epithelium and the blood.
What are alveoli EOU
-Tiny air sacs
-lots of them creating a large surface area for gas exchange - diffusion-
-the alveolar epithelial cells are very thin to minimize diffusion distance
- each alveolus is surrounded by a network of capillaries to remove exchanged gases and therefore maintain a concentration gradient.
Name two exchange surfaces in the human body
-small intestine
- alveoli
why do mammals have a specialized exchange surfaces
small SA:VR; therefore need specific exchange surfaces to maximize rate of exchange, They are to large so small SA:VR
to calculate SA:VR
-work out the the volume- if you can split the shape do that to calc the volume of both and add them together.
-to calc the surface area work out the area of all the shapes that have been split and add them together.
How does the tracheal system affect the max size of insects
diffusion- short diffusion pathway.
List three ways that insects are adapted to minimse water loss
-exoskeleton- waterproof.
-able to close spiracles
-large bodies therefore small SA:VR.
explain the importance of of countercurrent flow in fish
-equilibrium is not met, maintain gradient across the whole gill lamellae
for maximum diffusion
describe two similarities of gas exchange in a plant leaf and in insects
-minimize water loss
-both rely on diffusion
why do plant leaves have stomata
O2 out
CO2 in
list and explain the features of xerophytes which enable them to love in areas where there is little water
-Thick cuticle- traps water vapor
-roiled leaves- traps water vapor
-hairy leaves- traps water vapor
-stomata in pits/ shrunken stomata. -traps water vapor
-reduces SA:VR- less SA to loose water.
list the correct sequence that the air passes through on its journey from the gas exchange surface to the nose
- alveoli
-bronchioles
-bronchus
-trachea
-nose
Describe in detail what happens when you inhale and exhale. make references to muscles involved, volume changes and pressure changes.
- Intercostal muscles contract
2.Diaphragm contracts and flattens
3.volume increases and pressure decreases in the thoracic cavity - Air moves down pressure gradient
out:
1.external intercostal muscles relax
2.diaphragm relaxes and comes
3. volume decreases and pressure increases in thoracic cavity
4. air is forced out of the lungs
what is a correlation
one variable causes a change in another variable
Name three factors for lung disease
-viral factors
-smoking
-genetics
what is endopeptidase
An enzyme that hydrolyses peptide bonds between amino acids in the central region of protein.
Describe the process of glucose absorption in the small intestine
(5marks)
- sodium actively transported out of the cell into blood
2.higher concentration of sodium in the lumen in the cell
3.sodium diffuses into the cell down a concentration gradient with glucose.
4.Through a co-transport protein
5.glucose moves from the cell into the blood by facilitated diffusion
